Since we have this surety, being declared righteous through our faith in Christ's fulfillment of the promises of God based on the same thing being true of Abraham apart from the law and apart from circumcision, we therefore have peace with God the Father, through the Son, our Lord Jesus Christ: through Him, we have also obtained access by faith into this grace in which we stand (the righteousness of Christ imputed to us grants us right standing before God and adoption into His favor, the same favor the Son enjoys). Therefore, we boast (glory in, exult in) in the hope of the glory of God. Not only that, but we also boast in our sufferings, not boasting to each other about our endurance, but boasting in the purposes and providence of God that He grants and accomplishes through our sufferings.
We boast in our sufferings because, by God's power, suffering produces endurance because it is God who ordains suffering and works out His good purposes in it. We endure because we trust the One who has led us in and will lead us through it and turn it for good. In this way, suffering produces endurance. Endurance then produces character, and character, hope; and this is not a hope that will put us to shame because it is a sure hope (a settled future reality, not wishful thinking or wavering sentiments bound to falter), since God's love has been lavished upon us in the understanding of our hearts through the Holy Spirit who has been given to us, sent by the Father and the Son. Endurance, prolonged submission and obedience (persuasion, conformity) to the will of God produces growth in grace (character). Trial of the man of God (and faithful endurance in it) produces what Charles Hodge calls "tried integrity." And this wrought character within us strengthens our hope in the salvation and the coming glory of God, because of the surety of the promise to Abraham on our behalf, because of the confidence we have on account of what Christ has done for us.
This hope is not put to shame, not dashed, not shown hollow or ephemeral because we have been sealed with the Holy Spirit (God Almighty) on whom the hope of the promise rests (could He ever fail?), and He has lavished into our hearts the love of God. How then could we doubt? How could we doubt the love of God? How could we chalk it up to something, anything within us by which we commend ourselves to Him? While we were still weak, at the right time, Christ died for the ungodly (the very ones against whom the wrath of God is revealed from heaven). One would scarcely die for a righteous person, nary a sinner. But God shows His love for us in that while we were yet sinners, Christ died for us, the righteous One, for many sinners who rebelled against Him and hated Him. How great is the love of God! Greater than comprehension!
Therefore, since we have been justified by His shed blood, even more has He saved us from the wrath of God, our just penalty having fallen on Him. By His death we are reconciled to God; how much more shall we be saved by His glorious life? And as enemies having been reconciled by His death, how much more glorious will our salvation be by His life? And more than that, we exult, we glory, we boast, we rejoice in God, through our Lord Jesus Christ, through whom we have received this reconciliation!
God showed His great love for us in that one righteous Man died for many sinners, and in that one Man, the many have been reconciled to God and rejoice in Him. Therefore, it can be said that in the same way that sin came into the world and death through sin--by the trespass of one man, Adam--so also death spread to all men, for in Adam all died because in him all sinned by his one transgression. All sinned because the condemnation of all for a sin outside themselves (committed by Adam) rendered them sinners under him, their federal head. Sin, it's true, is a missing of the mark and one cannot strictly miss a mark never given, but while Adam's trespass and that of everyone from Adam to Moses were not strictly law-breaking, still they were trespasses of the command of God (they did not worship or serve or acknowledge Him as God, for they clearly perceived His attributes in that which He made, yet they did not see fit to acknowledge Him, exchanged the truth of God for a lie, and bowed down to His creations; Rom 1:20, 25, 28). So, while not breaking the law given through Moses (expressed in ordinances, Eph 2:15), they were still transgressing His righteous decree and falling short of His glory.
Death reigned over them, even though their sin was their own, not like the sin of Adam whose transgression opened the fountain of death for all men, a type of the one Man to come, whose righteousness would open the fountain of life for many. Christ's free gift, in a way, is like Adam's trespass, in that through one man a condition abounds for many; yet this similarity is disgraceful to make because Scripture here says that they are not alike, for in Adam the many died, but in Christ the many abound in the grace of God and in the free gift of grace in Christ, which the conclusion of Paul's argument in 5:21 makes clear leads to eternal life. The free gift and the trespass are as unlike one another as death is contrary to life.
Nor is the result of each similar: in Adam, condemnation, but in Christ, justification, because death has reigned through Adam's one trespass, while much more abounding grace and the free gift of righteousness reign in life through the one Man Jesus Christ. Therefore, as one trespass led to condemnation for all sinners, one act of righteousness (Christ's atoning death) leads to justification and life for all of God's elect; by Adam's disobedience (one man), the many were made sinners, and by Christ's obedience (one man), the many will be made righteous.
Now the law came in to increase the trespass (thereby to make men despair of righteousness by works of the law and prove it to be an impossibility for them to achieve). But where sin increased grace abounded all the more for there is more grace in Christ than there is sin in men; and it abounded, not on account of sin (a la Rom 3:7) but in spite of it and rather on account of the mercy of God, so that by the mercy of God, though sin reigned in death, grace might reign all the more through righteousness leading to eternal life through Christ Jesus our Lord.